\section{Conclusion}
\label{sec:conclusion}
In this paper, we proposed a novel dual-index (BFS and GFS) based data representation
based on our previous work partial tree for high-performance XML processing,
especially in terms of three classes of navigational XPath queries over very
large XML documents. The basis of this approach is the chunk-based fragmentation
and querying algorithms that exploit in-memory representation of chunks by
dividing an XML document. We also conducted several experiments on EC2
instances. The experiment results clearly showed the efficiency of our framework
outperform the state-of-the-art XML processing engine BaseX on 1 EC2 instance
and achieved the throughput of about 1 GB/s using 32 EC2 instances.

The current work has a configuration that all indices are storied in memory. Therefore,
our future work is to extend the ability of our implementation by developing new 
mechanisms to cooperate with modern distributed file systems, such as HDFS with 
MapReduce and related computing frameworks. In more details, we will pay our concern on data feeding, 
more expressive querying algorithms, error tolerance and etc.


%\section*{Acknowledgments}
%\label{sec:Acknowledgments}
